Squash intermediate git commits (and a cherry-picking shorthand)

git-squash-intermediates.md

Squashing intermediate commits, cherry-picking

You cannot directly squash earlier commits whilst retaining later ones.

Instead you need to create a picking branch, do some reset operations, re-commit the intermediary changes, and cherry-pick over the relevant commits. You must start from a clean state - no modifications, no staged items, no untracked files. Working tree clean must appear in your git status.

Below, my-branch-name is the name of the branch you are on.

1. Make a branch copy to perform the pick from - this also serves as a "backup" in case you need to abort squashing altogether/start again.
   • git branch pick/my-branch-name
2. Hard-reset the changes you DO want to keep - say you want to preserve the last 2 commits:
   • git reset --hard HEAD~2
3. Confirm that the commits to preserve still exist, and that your latest commits are the ones you want to squash
   • git log --all
   • (at this point, if you overshot, you can pull the changes back in and try again)
     • git pull . pick/my-branch-name
4. Then, soft-reset the commits you want to squash, say the last 3 commits, and make a new single commit
   • git reset HEAD~3 ; git log --all
   • if all is ok, proceed:
   • git add .
   • git commit -m "new commit message"
5. Now cherry-pick over the old commits from the pick branch
   • We use a couple of notations to specify the range from which to pick
     • relative commits notation with ~ to pick the second to last (my-branch-name~1) commit from the picking branch
     • We use the ^ to specify not to pick items from before the specified commit
     • we pick all the way up until the tip commit (my-branch-name itself)
   • git cherry-pick ^pick/my-branch-name~1 pick/my-branch-name
   • if you did it wrong, you can do git cherry-pick --abort here to bring your repository back to a clean state
   • git log --graph --all
6. Picking is now done, your intermediaries are squashed and your extra commits are restored. You can now delete the picking branch if you are happy
   • git branch -D pick/my-branch-name
7. If you need to scrap and try again, switch to the picking branch to use it as backup, delete your original branch, and then re-create it:
   • git checkout pick/my-branch-name
   • git branch -D my-branch-name
   • git branch my-branch-name
   • git checkout my-branch-name
   • git log
   • Then, return to step 2